Sun Lecture

  1. Bulk Properties
  2. Fill in Vital Statistics, except Luminosity
  3. Show the TRACE Photographs
  4. Read the description of the Sun from Warren’s Recreations in Astronomy, 1879
  5. Define Luminosity
  6. Maintenance of Solar Heat
  7. Read “On the Maintenance of Solar Heat” from Young’s Lesson’s in Astronomy, 1903
  8. Energy Source of the Sun
  9. Nuclear Fusion: The Proton-Proton Chain
  10. 4p1He + 2 +7
  11. 7 are “thermalized” by the time they reach the surface
  12. Energy generated from Mass Loss

Initial Mass of 4p:6.6943x10-27 kg

Final Mass of 1He:6.6466x10-27 kg

Mass Lost = 0.0477x10-27 kg

  • Mass is converted into Energy through Einstein’s E=mc2
  • How much mass must be converted into Energy each second?

E/t = mc2/t =L

m/t =L /c2 = 4,3 x 109 kg/sec

= 4.3 Million metric tons per second!

  1. Two Layer Model of the Sun (See Interior of Sun Handout)
  2. Core
  3. Envelope
  4. Weight lifter Analogy
  5. The Lifetime of the Sun
  6. How long can the Sun continue to lose mass at this rate?
  7. Personal Weight Loss Analogy
  8. Estimated Lifetime of the Sun = M/(m/t)

T = 1.99x1030 kg/4.3x109 kg/sec

= 4.62x1020 sec

= 15 Trillion years

  • The more correct answer is 10 Billion year lifetime, with about 5 Billion to go
The Sun
Vital Statistics

Definition of luminosity: ______

______

Source of the Sun’s Luminosity is ______

Implications of the Sun’s Luminosity:

  • The Sun produces energy by converting mass into energy.
  • The luminosity of the Sun thus represents a continual mass loss.
  • The Sun is currently converting 4.3 million metric tones of mass into energy each second.
  • How long can the Sun maintain this rate of mass loss?

Simple answer: ______

More accurate answer: 10 Billion years.


Two Layer Model of the Sun

Property

/ Core / Envelope
Radius / ~Inner 20% / ~Outer 80%
Volume / ~1% of Solar Volume / ~99% of Solar Volume
Mass / ~1/3rdof Total Mass / ~2/3rdsof Total Mass

Density

/ ~100 gm/cm3 / ~1 gm/cm3
Temperature / 15 Million K / 5,800 K

The function of the core is to produce energy and support the envelope. The envelope’s function is to contain the core and maintain core conditions so energy can continue to be produced. The envelope is also involved in the thermalization of core gamma rays. Note the envelope can be further subdivided into an inner radiative zone and an outer convective zone based on the method or energy transport to the photosphere. The sun is currently in near hydrostatic equilibrium where the gravitational forces from the weight of the envelope is equal and opposite to the thermal expansion forces due to energy production in the core.